The invention relates to a device for an apparatus for electrical discharge machining, of the type comprising means for displacing the electrodes relative to one another in translation in two directions perpendicular to an axis of penetration of the tool in the workpiece, means for imparting to the electrodes a given relative movement in the plane of this translation, means for transmitting to the amplitude of this translational movement the relative movements of the electrodes towards and away from one another along said axis of penetration of the tool in the workpiece, said movements being controlled so as to maintain given sparking conditions in the machining zone comprised between the electrodes.
Such a device is described, for example, in U.S. Pat. No. 3 539 754 and enables machining of the lateral surfaces of the workpiece to a different shape than the shape of the tool. The machined shape, which is, for example, determined by the factor of proportionality between the amplitude of the translational movement and the axial displacement of the tool, corresponds to the shape of an envelope of the trajectories during the cyclic translational movements.
An other device, with which an orifice of increasing conicity is machined with a tool in the form of a flat disc, is described in W. German published patent application (DOS) No. 2 238 698. Theoretically, this last device could be used for producing a three-dimensional dilatation of the tool electrode in order to machine a recess having substantially the same shape as the tool. However, this device is complicated and comprises numerous mechanical parts connected one to the other, so that it would be mostly inoperative for imparting to the tool the very short displacement which must be effected very quickly and with accuracy when machining simultaneously the front and lateral faces of a recess with a dilated electrode tool.
The invention aims to provide a new device, which can be easily manufactured and which displaces the electrode with the desired stiftness and accuracy.
The accompanying drawings show, schematically and by way of example, two embodiments of the device according to the invention.